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Check usb_busy up front in usb background function.

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Waiting to do so risks accidentally queueing another response.

Hopefully fixes #655 but we'll let @jerryneedell confirm.
This commit is contained in:
Scott Shawcroft 2018-03-14 10:32:41 -07:00
parent b64d568267
commit 7a3f86d184
1 changed files with 9 additions and 2 deletions
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11
ports/atmel-samd/usb_mass_storage.c
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@ -280,7 +280,14 @@ int32_t usb_msc_xfer_done(uint8_t lun) {
// drive into our cache and trigger the USB DMA to output the
// sector. Once the sector is transmitted, xfer_done will be called.
void usb_msc_background(void) {
if (active_read && !usb_busy) {
// Check USB busy first because we never want to queue another transfer if it is. Checking
// active_read or active_write first leaves the possibility that they are true, an xfer done
// interrupt occurs (setting them false), turning off usb_busy and causing us to queue a
// spurious transfer.
if (usb_busy) {
return;
}
if (active_read) {
fs_user_mount_t * vfs = get_vfs(active_lun);
disk_read(vfs, sector_buffer, active_addr, 1);
CRITICAL_SECTION_ENTER();
@ -288,7 +295,7 @@ void usb_msc_background(void) {
usb_busy = result == ERR_NONE;
CRITICAL_SECTION_LEAVE();
}
if (active_write && !usb_busy) {
if (active_write) {
if (sector_loaded) {
fs_user_mount_t * vfs = get_vfs(active_lun);
disk_write(vfs, sector_buffer, active_addr, 1);